JP3131029B2 - Aluminum nitride substrate and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride substrate in which a metallized layer in which aluminum nitride is uniformly dispersed in a high melting point metal and a plating layer are sequentially laminated, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the joining of ceramic bodies to metals has played a very important role in the complex industrial technology of materials. That is, with the development of a new material for the ceramic body, attention has been paid to aluminum nitride having excellent properties not available in the conventional oxide ceramic body, for example, high thermal conductivity,
For example, application to substrates for electronic components and semiconductor components has been promoted. Further, when used as a substrate, it is necessary to form a wiring layer on the substrate, and excellent strength is required for bonding such a ceramic body to a metal.

[0003] In recent years, a method of manufacturing an aluminum nitride (AlN) substrate has been proposed, for example, by applying a metallizing paste containing a refractory metal and AlN to the surface of an AlN molded body, and applying the metallized paste in a non-oxidizing atmosphere. It is performed by co-firing at a predetermined temperature (Japanese Unexamined Patent Publication No.
No. 291480).

[0004] Then, a metallized layer of the AlN sintered body is plated with nickel to form a metal layer on the surface of the AlN sintered body, and pins are soldered to the metal layer, for example, as a package to be incorporated into a substrate. Used. Such a package is also a substrate.

[0005]

However, in the above-described method for manufacturing an AlN-based substrate, AlN is exposed on the surface of the metallized layer at the time of firing, so that the plating cannot be performed completely. there were.

That is, in order to increase the metallizing strength, about 1 to 5% by weight of the porcelain material (A
When 1N) is added, AlN tends to appear on the surface of the metallized layer during firing. Since the exposed AlN and nickel of the plating material have low wettability, voids are generated in the nickel plating layer, and there is a problem that the plating process cannot be performed completely.

[0007] For this reason, there is a problem that voids are formed which are not covered even by Au plating to be performed later, and a plating solution or moisture is trapped in the voids to form nickel hydrate, thereby causing corrosion of nickel. Also, due to the existence of such voids, the solder (silver) of the solder layer
There was also a problem of corrosion. As a result, there are problems that the characteristics of the porcelain and the reliability when used as a package are deteriorated, and that the porcelain is discolored.

The present invention has been made to solve the above problems and the like, and has as its object to provide an AlN-based substrate capable of minimizing voids in a plating layer and a method of manufacturing the same. .

[0009]

Means for Solving the Problems The present inventors have studied the above phenomenon and found that the metallized layer formed on the surface of the AlN sintered body was subjected to a predetermined surface treatment, and the surface of the metallized layer was treated. The present inventors have found that voids in the plating layer can be suppressed to a minimum by removing the aluminum nitride exposed in the method described above or by reducing the diameter of the aluminum nitride on the surface of the metallized layer.

That is, the aluminum nitride substrate of the present invention is an aluminum nitride substrate in which a metallized layer in which aluminum nitride is dispersed in a high melting point metal and a nickel plating layer are sequentially laminated. Aluminum nitride does not substantially exist on the layer side surface , or the maximum diameter of aluminum nitride is 2 μm or less
It is characterized by being.

The reason why the maximum diameter of AlN present on the surface of the metallized layer on the plating layer side is set to 2 μm or less is that when the maximum diameter of AlN is larger than 2 μm, the wettability between the exposed AlN and the nickel of the plating material is reduced. This is because AlN cannot be completely covered when plated, and voids occur in the plated layer. This is because, when the maximum diameter of AlN on the surface of the metallized layer is suppressed to 2 μm or less according to the present invention, the occurrence of voids as described above is reduced, and plating can be performed almost completely. In particular, it is preferable that AlN is not substantially present on the surface of the metallization layer on the plating layer side.

Further, in the method of manufacturing an aluminum nitride substrate according to the present invention, a metallized layer containing a refractory metal and aluminum nitride is formed on the surface of an aluminum nitride sintered body, and then the aluminum nitride on the surface of the metallized layer is formed. The phosphorus
Removed with an acid compound solution , or reduced the diameter of aluminum nitride on the surface of the metallized layer to a maximum diameter of 2 μm or less.
After that , a nickel plating layer is formed on the surface of the metallized layer.

As the surface treatment of the metallized layer, a method of removing AlN with a sand blast or a brush or performing an acid treatment is known. According to the present invention, the metallized layer is treated with a phosphoric acid compound solution. By treating with this phosphoric acid compound solution, the level of AlN removal can be controlled. As the phosphoric acid compound liquid, for example, H ₃ PO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ or the like is used.

The aluminum nitride sintered body used in the present invention may be, for example, an AlN powder as a main component and an auxiliary component,
After the solvent is sufficiently mixed by a ball mill and formed into a predetermined shape, the mixture is heated to 1600 to 1950 ° C. in a non-oxidizing atmosphere.
And formed by firing.

On the other hand, as the high melting point metal in the metallized layer, for example, metal elements of the periodic table Nos. 4a, 5a and 6a are known.

[0016]

According to the AlN substrate of the present invention and the method for manufacturing the same,
Since the surface of the metallized layer was treated before forming the plated layer, AlN exposed on the surface of the metallized layer was removed before plating, or the maximum diameter of the metallized layer was 2 μm or less. Since only AlN exists,
The wettability between the plating layer and the metallized layer is improved, and the generation rate of voids in the plating layer can be suppressed to a minimum.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG.
This shows the aluminum nitride substrate of the present invention.
Reference numeral 1 denotes an AlN sintered body. This AlN sintered body 3
A metallized layer 33 in which AlN is dispersed in a refractory metal is formed on the surface of the metallized layer 1, and a plating layer 37 is formed on the surface of the metallized layer 33.

FIGS. 2 to 4 are process diagrams for explaining the method of manufacturing an AlN substrate according to the present invention.

In the method of manufacturing an AlN substrate according to the present invention, first, as shown in FIG. 2, a metallized layer 33 containing a refractory metal and AlN is formed on the surface of an AlN sintered body 31. That is, AlN powder as the main component (average particle size of 1-2 μm)
m) and oxides, nitrides, carbides, borides and the like of the elements of Group 2a and 3a of the Periodic Table such as Y ₂ O ₃ and CaO as sintering aids. The agent, dibutyl phthalate, and a binder are added, mixed sufficiently by a ball mill or the like, and formed into a plate shape by a doctor blade method or the like. The AlN compact is formed, for example, by containing 90 to 95% by weight of AlN powder and 5 to 10% by weight of sintering aid powder.
Periodic tables 4a, 5a, 6 of i, Ta, V, W, Mo, etc.
In some cases, a compound of a group a element is added at a ratio of 10% by weight or less.

Then, after applying a metallizing paste containing a refractory metal and AlN to a predetermined surface of the AlN molded body by screen printing or the like, the temperature is raised to 1 ° C. in a non-oxidizing atmosphere.
By simultaneously firing at 800 to 1900 ° C., AlN
Metallized layer 33 is formed on the surface of sintered body 31. As another method, after producing an AlN sintered body,
It is formed by applying a paste mainly composed of a refractory metal and AlN and baking it at a predetermined temperature.

The metallized layer 33 is made of, for example, 95 to 99% by weight of a high melting point metal, 1 to 5% by weight of AlN, and in some cases the periodic table 2a, 3 known as an auxiliary agent of AlN.
oxides, nitrides, carbides, borides, etc. of group a elements
0.5% by weight.

As the high melting point metal, for example, W, Mn,
Periodic tables 4a, 5a, 6a, 7 of Mo, Ti, Ta, etc.
Group a metal elements and the like are used.

The oxides, nitrides, carbides and borides of the elements of Groups 2a and 3a of the Periodic Table contained in the AlN sintered body or the metallized layer include Y ₂ O ₃ and Yb.
_{There are 2} O ₃ , Er ₂ O ₃ and CaCO ₃ and others.

The metallized layer 3 thus formed
X-ray diffraction measurement confirmed that AlN35 having a maximum diameter b larger than 2 μm was precipitated on the surface of No. 3 as shown in FIG.

After the metallized layer 33 is formed on the AlN sintered body 31, the metallized layer 33 is subjected to a surface treatment to remove AlN on the surface of the metallized layer 33 or to reduce the diameter of AlN on the surface of the metallized layer 33. Thereafter, plating is performed.

For the surface treatment of the metallized layer 33, a method using a phosphoric acid compound solution is used. Hereinafter, an example using the phosphoric acid compound will be described.

In order to treat the AlN on the surface of the metallized layer 33, as shown in FIG. 3, the surface treatment of the metallized layer 33 is performed by immersing the AlN sintered body 31 in a water tank containing a phosphoric acid compound solution. . This phosphoric acid compound solution includes H ₃ PO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , (NH
₄ ) ₂ HPO _{4 and the} like are known, and the phosphoric acid compound solution to be used is determined based on the amount of AlN 35 exposed on the metallized layer 33. H ₃ PO ₄ is 3
Since the dissociation is performed in stages, the degree of removal of AlN 35 exposed on the metallized layer 33 can be controlled by the phosphoric acid compound used. That is, H ₃ PO ₄ becomes H
₃ PO ₄ → KH ₂ PO ₄ → K ₂ HPO ₄ dissociates in three steps, and KH ₂ PO ₄ becomes KH ₂ PO ₄ → K ₂ HPO ₄ and 2
If there is much AlN 35 to be removed from the surface of the metallized layer 33 to dissociate into stages, use H ₃ PO ₄ ,
If less, K ₂ HPO ₄ is used.

Thereafter, the metallized layer 33 is plated with nickel or the like to form a plated layer 37 as shown in FIG. Examples of the plating process include electroless plating and electrolytic plating. A pin 39 made of Kovar is fixed to such a plating layer 37 with silver wax or solder 41, and is used as a package to be incorporated into a substrate.

In the AlN substrate configured as described above, before forming the plating layer 37 on the metallized layer 33,
Since the surface of the metallized layer 33 has been subjected to surface treatment, AlN 35 is removed from the surface of the metallized layer 33 before plating, or the diameter of AlN 35 on the surface of the metallized layer 33 is reduced, so that the metallized layer 33 and the plating layer 37 become wet. Thus, the generation of voids in the plating layer 37 is suppressed. Therefore, unlike the conventional case, almost no voids are formed in the plating layer 37, so that nickel and silver are hardly corroded therefrom, and the porcelain characteristics and the reliability when used as a package can be improved. It is possible to prevent discoloration of the porcelain and the like.

When a phosphoric acid compound solution is used as a surface treatment liquid for the metallized layer 33, the surface of the AlN sintered body 31 is hardly eroded, and AlN 35 only on the surface of the metallized layer 33 can be removed. In addition, it is possible to improve the reliability when used as a package or a package, and to prevent discoloration of porcelain. Furthermore, since the phosphoric acid compound solution dissociates in three steps in an aqueous solution,
The degree of removal of AlN 35 exposed on metallized layer 33 can be controlled by the type of solution used.

After forming the AlN sintered body 31, the metallized layer 33 may be subjected to a surface treatment with a phosphoric acid compound solution.

Example 1 An AlN powder (average particle size of 1-2 μm) as a main component was mixed with 90
_{Wt%, Er 2 O 3, CaCO} 3 a sintering aid powder consisting of 10 wt% and a dispersant and a plasticizer added, thoroughly mixed by a ball mill, molding it into a plate shape by a doctor blade method.

Tungsten is applied to a predetermined surface of the compact
5% by weight, 0.5% by weight of Er ₂ O ₃ and CaCO ₃
And a metallized paste containing 4.5% by weight of AlN, and then at a temperature of 1800 ° C. in a non-oxidizing atmosphere.
To form a metallized layer having a thickness of 20 μm on the surface of the AlN sintered body. According to the result of X-ray diffraction measurement of the surface of the metallized layer, as shown in FIG. 2, the appearance of AlN having a maximum diameter b larger than 2 μm was observed in spots.

The surface of the metallized layer thus formed is subjected to a surface treatment with H ₃ PO ₄ and KH ₂ PO ₄ , and then nickel-plated, and a thickness of 2 μm is formed on the surface of the metallized layer.
Is formed. A pin made of Kovar was brazed to this plating layer. The surface treatment of the metallized layer is performed by immersing the sintered body on which the metallized layer is formed in a phosphate compound solution. Here, in the case of surface treatment with H ₃ PO ₄ is 30 in a solution of a temperature 70 ° C. to H ₃ PO ₄ contains 1 mol in 1 liter
When the surface treatment was carried out by immersion in KH ₂ PO ₄ for 30 minutes, the phosphoric acid compound was immersed in a 70 ° C. solution containing 1 mol per liter for 30 minutes. The maximum diameter b of AlN after the surface treatment is 2 μm or less,
It was confirmed by the X-ray diffraction measurement result.

Then, the metallizing strength was measured by pulling the pin. The results are shown in the line graphs of FIGS. 5 and 6 in which the vertical axis represents the metallization strength and the horizontal axis represents the immersion time.

FIG. 5 shows that when the treatment liquid was KH ₂ PO ₄ , it was almost constant irrespective of the immersion time in the treatment liquid, but when the treatment liquid was H ₃ PO ₄ , As shown in the figure, when the processing time is 20 minutes, the metallization strength is sharply reduced. This is considered to be due to the fact that when immersed in H ₃ PO ₄ for 20 minutes or more, the etching of the AlN sintered body itself proceeds and the strength is deteriorated.

In FIGS. 5 and 6, when the pin was pulled, the pin finally peeled off in the metallized layer. Furthermore, KH
_{When the} surface treatment was performed with ₂ PO ₄ , the AlN sintered body was hardly dissolved, and it was confirmed that only AlN on the surface of the metallized layer was dissolved, but when the surface treatment was performed with H ₃ PO ₄ , It was confirmed that the AlN sintered body was slightly dissolved. Thereby, in the first embodiment, H ₃ PO ₄
The solution turns out to be too strong.

The case where the surface treatment of the metallized layer is not performed, the case where the AlN sintered body is immersed in a solution containing 1 mol of KH ₂ PO ₄ per liter at a temperature of 70 ° C. for 50 minutes, The above AlN-based sintered body was added to a solution containing 1 mol of KH ₂ PO ₄ in 1 liter at a temperature of 70 ° C.
In the case of immersion for a minute, the void area in the plating layer was measured by an ultrasonic flaw detector. Void area ratio in the case of no treatment but was 10% when immersed for 50 minutes in KH ₂ PO ₄ solution of 70 ° C. was 0% 70 ° C. of KH ₂ PO
_{4 It} is 1% when immersed in the solution for 30 minutes, and it is understood that the void area ratio becomes 1% or less when the method for manufacturing an aluminum nitride substrate of the present invention is used.

Example 2 A metallized layer having a thickness of 20 μm was formed on the surface of the AlN sintered body in the same manner as in Example 1 above. According to the X-ray diffraction measurement result of the surface of the metallized layer, the maximum diameter is 2 to 4 μm.
The appearance of mN AlN was observed as spots.

Then, after performing the surface treatment of the metallized layer by various surface treatment methods, a plating layer was formed and the pins were brazed. Then, as in Example 1, the void area ratio and the metallized strength were measured, and the maximum diameter of AlN after surface treatment of the metallized layer was measured by X-ray diffraction measurement.

As a result, an experiment in which the surface treatment was performed by sandblasting a plurality of times showed that A having a maximum diameter of 2 to 4 μm was used.
The surface of the metallized layer where 1N was
Had a maximum diameter of 1.5 to 2.0 μm, a void area ratio of 1%, and a metallized strength of 6.5 kgf.

When the surface treatment with the phosphoric acid compound was carried out several times, the surface of the metallized layer in which AlN having a maximum diameter of 2 to 4 μm was present had a maximum diameter of 1.0 to 1.0 μm. The void area ratio was 0%, and the metallization strength was 6.3 kgf.

Further, as a comparative example, when an experiment without surface treatment was performed a plurality of times, the maximum diameter of the A was 2 to 4 μm.
The surface of the metallized layer where 1N was
The maximum diameter of 1N is 2-4 μm and the void area ratio is 10
%, And the metallized strength was 6.7 kgf.

From these results, it is found that when the maximum diameter of AlN after the surface treatment of the metallized layer is 2 μm or less, the void area ratio is 1% or less.

[0045]

As described above in detail, in the AlN substrate and the method of manufacturing the same according to the present invention, the surface of the metallized layer is treated before forming the plated layer.
AlN exposed on the surface of the metallized layer has been removed,
Alternatively, A having a maximum diameter of 2 μm or less
Since only 1N is present, the wettability between the plating layer and the metallized layer is improved, and the rate of occurrence of voids in the plating layer can be suppressed to a minimum, thereby improving the porcelain characteristics and reliability when used as a package. In addition to improving the performance, it is possible to reliably prevent discoloration of the porcelain.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an AlN substrate of the present invention.

FIG. 2 is a vertical sectional view showing an example in which a metallized layer is formed on an AlN sintered body.

FIG. 3 shows A having a metallized layer formed in a phosphoric acid compound solution.
It is explanatory drawing which shows the state which dipped the 1N quality sintered compact.

FIG. 4 is a longitudinal sectional view showing an example in which a pin is brazed to an AlN sintered body.

FIG. 5 is a line graph showing the relationship between metallization strength and immersion time in a KH ₂ PO ₄ solution.

FIG. 6 is a line graph showing the relationship between metallization strength and immersion time in an H ₃ PO ₄ solution.

[Explanation of symbols]

 31 AlN sintered body 33 Metallized layer 35 AlN 37 Plating layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-104904 (JP, A) JP-A-3-36282 (JP, A) JP-A-53-142327 (JP, A) 141169 (JP, A) JP-A-2-18753 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 41/80-41/91

Claims (2)

(57) [Claims] An aluminum nitride substrate in which a metallized layer in which aluminum nitride is dispersed in a high melting point metal and a nickel plating layer are sequentially laminated, and aluminum nitride is formed on the surface of the metallized layer on the plating layer side. It is substantially absent or the maximum diameter of aluminum nitride is 2μ
m or less . Wherein the surface of the aluminum nitride sintered body forming a metallized layer containing high melting point metal and aluminum nitride, and then phosphorus aluminum nitride of the metallized layer surface
Removed with an acid compound solution , or reduced the diameter of aluminum nitride on the surface of the metallized layer to a maximum diameter of 2 μm or less.
And forming a nickel plating layer on the surface of the metallized layer.